Yeah. While every other manufacturer uses cameras and light reflection, Tesla proudly touts an often broken AI model for recognizing rain. It is a huge source of complaint - the auto function doesn't work with any degree of reliability for many users.
Pretty well. The only challenge I've ever seen on my cars (Nissan, Jaguar, multiple Audis, not at the same time) is when its standing water on the windshield and often grey mornings, when there's not much light to trip the light reflection aspect. But that's a small price to pay. My current Audi has variable intermittent wipers (i.e. there's off, intermittent*, steady, fast, where intermittent has three settings in itself) where you can toggle between timer-based intermittency and rain sensor-based (that toggle is via the MMI console, the rest is on the stalk).
